1. Field of Invention
The present invention relates to a system for switching optical signals through free space. More particularly, the present invention relates to a system for switching optical signals between an optical transmission device, such as an optical fiber, and an end user or node that is separated from the optical transmission device by a distance of free space.
2. Description of Related Art
Optical communication systems are a substantial and rapidly growing part of communication networks. The expression xe2x80x9coptical communication system,xe2x80x9d as used herein, relates to any system that uses optical signals to convey information across an optical transmission device, such as an optical fiber. Such optical systems may include, but are not limited to telecommunication systems, cable television systems, and local area networks (LANs).
While the need to carry greater amounts of data on optical communication systems has increased, the capacity of existing transmission devices is limited. Although capacity may be expanded, e.g., by laying more fiber optic cables, the cost of such expansion is prohibitive. Consequently, there exists a need for a cost-effective way to increase the capacity of existing optical transmission devices.
Wavelength division multiplexing (WDM) has been adopted as a means to increase the capacity of existing optical communication systems. In a WDM system, plural optical signals are carried over a single transmission device, each channel being assigned a particular wavelength.
An essential part of optical communication systems is the ability to switch or route signals from one transmission device to another. Designers have considered using bubbles that are capable of changing their internal reflection for switching optical signals. However, this technique is unable to switch multiple wavelengths individually. Micro-electromechanical mirrors are capable of switching optical signals. However, these mirrors have not been successfully adapted for use in a WDM system. Furthermore, both of these devices have limited switching speeds, in the range of 10 kHz for the mirror devices and in the range of 100 Hz for the bubble devices.
Other switching approaches, such as the approach disclosed in U.S. Pat. No. 4,769,820, issued to Holmes, can switch data at GHz rates, which is effectively switching at GHz transition rates. However, this approach requires substantial optical switching power, has potential cross talk, and cannot resolve wavelength over-utilization issues. What is needed is a means for switching wavelength division multiplexed signals that is capable of doing so at high speeds with no cross talk and requires low switching power.
Another problem faced by current optical communication systems is transmission of signals between end users and optical fibers. Optical fibers have not been laid to most buildings and most buildings do not have optical fiber installed in them. It would be very expensive to lay optical fiber to every building that should be connected to an optical communication network and it would be more expensive still to retrofit existing buildings with optical fiber so that users in the building can be directly connected to the network.
To overcome this problem, edge switches have been developed for use with optical systems. Edge switches are switches that transmit signals between one or more transmission devices and one or more end users. Existing edge switch products include Cisco Edge Services Router 10000, HP ProCurve 2524, SMC Barricade 11 Mbps Wireless Broadband Router, and Linksys Broadband Etherfast Cable/DSL Router. These systems have as many as 24 ports for high-speed inputs that distribute signals to as many as 250 users. However, none of these systems are purely optical, e.g., they do not transmit optical signals to the end users.
Some of these devices utilize wireless technology to transmit signals between the optical system and the end user. However, wireless connections have limited total capacity, about 4 Gbits/sec at most. Optical free-space interconnects are being developed by Nortel and Terabeam for building-to-building interconnections.
U.S. patent applications titled Method and Device for Switching Wavelength Division Multiplexed Optical Signals Using Emitter Arrays, filed on Sep. 20, 2000, incorporated herein by reference, discloses a high-speed optical switch. This switch may comprise a plurality of switch elements, each switch element being capable of detecting and emitting a range of wavelengths. The invention is capable of switching signals in any number of wavelengths between any number of fibers that may be in different spatial positions. As will be discussed below, this switch may be used to switch optical signals between an optical transmission device and other devices or end users that are separated from the optical transmission device by a distance of free space.
An advantage of the present invention is that it allows end users to communicate over an optical communication system with a free space connection.
Another advantage of the present invention is that it allows end users to communicate over an optical communication network without having contiguous optical fiber laid to the end users.
Another advantage of the present invention is that end users may communicate with an optical communication system without installing optical fibers in buildings or other structures where the end users are located.
Another advantage of the present invention is that it provides an edge switch that is capable of communicating with a very large number of end users or nodes.
A further advantage of the present invention is that it provides an optical edge switch that may communicate with an end user or node in a wavelength that is different than the wavelength used by the communication system.
Yet another advantage of the present invention is that it provides a high-speed edge switch that is capable of utilizing wave division multiplexing.
These and other advantages of the present invention may be realized by reference to the remaining portions of the specification, claims, and abstract.
The present invention comprises an optical switch for switching optical signals between a plurality of nodes and at least one optical fiber. The optical switch comprises at least one switch element and a mirror.
The switch element comprises at least one detector array, at least one emitter array, and at least one controller. The detector array is positioned to receive optical signals transmitted by the optical fiber and the nodes, rhe emitter is positioned to transmit optical signals to the plurality of nodes and the optical fiber, and the controller is in communication with the detector array and the emitter array. The controller is adapted to cause the emitter array to transmit the optical signal transmitted by the optical fiber.
The mirror is being positioned to reflect optical signals between the switch element and the plurality of nodes. The mirror is adapted to reflect optical signals between the switch element and the plurality of nodes, wherein the optical signal transmitted by the emitter array of the switch element is reflected to at least one of the plurality of nodes and an optical signal transmitted by at least one of the plurality of nodes is transmitted to the detector of the switch element.
The above description sets forth, rather broadly, the more important features of the present invention so that the detailed description of the preferred embodiment that follows may be better understood and contributions of the present invention to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and will form the subject matter of claims. In this respect, before explaining at least one preferred embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and to the arrangement of the components set forth in the following description or as illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.